1. Field of the Invention
The present invention relates to an image forming apparatus to form images using toner, such as a laser printer, copier or the like, and more particularly, to a method and an apparatus to form images efficiently using toner by which images are formed at high speed.
2. Description of the Related Art
A conventional image forming apparatus using toner is described as follows.
A conventional image forming apparatus, for example, a laser printer, is comprised of a video controller (not shown), and a printer engine (not shown). Here, the video controller is comprised of a data transmitting/receiving portion (not shown) to receive image data transmitted from a host (not shown), and an image rendering portion (not shown) to perform rendering operations, such as reconstructing the received image data into dot data. At this time, the printer engine receives the rendered data output from the video controller, feeds a sheet, and forms an image on the fed sheet.
Here, in the printer engine, an image forming speed, i.e., a printing speed of an image, varies with a feeding speed of a sheet. For example, the printer engine satisfies a required PPM (pages per minute) by adjusting the speed of an engine motor and an interval between successive sheets. At this time, when the speed of the motor is set to be faster or the time interval between sheets is set to be shorter, the PPM is increased so that an image may be formed faster. However, there is a problem in which a jam may occur easily due to the shorter interval of feeding sheets so that an image cannot be formed normally. Here, a jam is an event in which, while a previous sheet is feeding, the next sheet is feeding together with the previous one or in which the next sheet is partially overlapping the previous one. Therefore, there is a limitation in increasing an image forming speed by simply increasing the motor speed.
In other words, to precisely meet the required PPM, a conventional image forming apparatus using toner repeatedly performs an operation of feeding a sheet from a sheet cassette at a predetermined interval of time. That is, the conventional image forming apparatus using toner feeds each sheet always at the same interval of time when sheets of the same size are continuously used to form a series of images. Therefore, in the conventional image forming apparatus using toner, there is a limitation in increasing the image forming speed only by increasing the speed of the engine motor without shortening the time interval between successive sheets.